Alloy surface segregation in reactive environments: A first-principles atomistic thermodynamics study of Ag3Pd(111) in oxygen atmospheres

TL;DR

This study develops a first-principles thermodynamics framework to analyze how alloy surfaces, specifically Ag3Pd(111), segregate and interact with oxygen atmospheres, revealing complex adsorption behaviors and the importance of non-stoichiometry.

Contribution

The paper introduces a novel atomistic thermodynamics approach to predict alloy surface segregation in reactive environments, incorporating non-stoichiometry effects for the first time.

Findings

Oxygen adsorption energies vary widely across alloy configurations.

Strong oxygen binding observed on some alloy surfaces, exceeding Pd(111).

Non-stoichiometry significantly influences Pd surface segregation in oxygen-rich environments.

Abstract

We present a first-principles atomistic thermodynamics framework to describe the structure, composition and segregation profile of an alloy surface in contact with a (reactive) environment. The method is illustrated with the application to a Ag3Pd(111) surface in an oxygen atmosphere, and we analyze trends in segregation, adsorption and surface free energies. We observe a wide range of oxygen adsorption energies on the various alloy surface configurations, including binding that is stronger than on a Pd(111) surface and weaker than that on a Ag(111) surface. This and the consideration of even small amounts of non-stoichiometries in the ordered bulk alloy are found to be crucial to accurately model the Pd surface segregation occurring in increasingly O-rich gas phases.